You may be able to cycle to work therefore reducing pollution
Cycling improves lung function
Cycling is fun and can be a shared exercise
Bicycles are on sale in many main street retailers but if your bike is old you should make sure it is in good condition and road worthy by performing regular maintenance. Never cycle after dark without lights. Carry a basic toolkit with you and a spare inner tube for emergencies.
Make sure you follow the highway code and wear a safety helmet at all times.